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TEChNOLOGY

A chemical process that could make as polysulfates

esearchers have developed a chemical process that that specializes in nanoscale science, worked with a
Rcould make a class of polymers known as polysulfates team led by Sharpless and Peng Wu, professors at the
more competitive with polycarbonates – sturdy plastics Scripps Research Institute (TSRI). The team created long
that can form structural panels like the ones pictured chains of linked sulfur-containing molecules, termed
here. Such panels can be used as building materials. A polysulfates and polysulfonates, using a SuFEx click
team of researchers has developed a faster and easier reaction. "Click chemistry is a powerful tool for materials
way to make sulfur-containing polymers that will lower discovery, but synthetic chemists are often not well-
equipped to characterize the polymers they create,” said
the cost of large-scale production. The achievement, Yi Liu, director of the organic Synthesis facility at the
published in Nature Chemistry and Angewandte Chemie, Molecular Foundry. “We can provide a broad spectrum
of expertise and instrumentation that can expand the
scope and impact of their research."
The SuFEx reaction, introduced as a new family of click
reactions in 2014, reliably and quickly creates new
chemical bonds, connecting compounds together with
sulfates or sulfonates. While polysulfates have shown
great potential as competitors to polycarbonates (strong
plastics used for eyewear lenses and water bottles, for
example), they have been rarely used for industrial
applications due to a lack of reliable and easily scalable
synthetic processes. To overcome the challenges of mass-
manufacturing polysulfates and polysulfonates, the TSRI
team explored various catalysts and starting reagents to
opens the door to creating new products from this class optimize the SuFEx reaction.
of polymers while producing far less hazardous waste. They relied on their collaborators at the Molecular
The researchers’ reaction technique, dubbed SuFEx for Foundry to assess physical properties and determine
sulfur(VI) fluoride exchange, combined with a newly if the newly created polymers were thermally stable
identified class of catalysts that speed up the reactions, products. Polymers are assembled from smaller
could be used to make everything from water bottles and molecules – like stringing a repeating pattern of beads
mobile phone cases to medical devices and bulletproof on a necklace. In creating a polysulfonate “necklace”
glass. When a useful molecule is discovered, there are few with SuFEx, the researchers identified ethenesulfonyl
reactions that chemists can use that are simple and efficient fluoride-amine/aniline and bisphenol ether as good
“beads” to use and found that using bifluoride salt as a
enough to meet the industrial production requirements catalyst made the previously slow reaction “click” into
for cost-effectively scaling up. In 2001, Nobel laureate action. Researchers found that the high efficiency of the
K. Barry Sharpless introduced a new concept to organic reaction results in a remarkable 99 percent conversion,
chemistry known as “click chemistry,” describing a suite of from starting reactants to products, in less than an hour.
controllable, highly reactive reactions that are high-yielding Researchers found that the new reaction requires 100
and require little to no purification. to 1,000 times less catalyst than other known methods,
Following nature’s example, click reactions follow simple resulting in significantly less hazardous waste. Bifluoride
protocols, use readily available starting materials, salts are also much less corrosive than previously used
and work under mild reaction conditions with benign catalysts, allowing for a wider range of starting substrate
starting reagents. Click chemistry has become a valuable “beads,” which researchers said they hope could lead to
tool for generating large libraries of potentially useful its adoption for a range of industrial processes. “There
compounds as industries look to discover new drugs and are many new polymers that haven’t been widely used
materials. Scientists at Lawrence Berkeley National by industry before,” said Liu.
Laboratory’s (Berkeley Lab) Molecular Foundry, a facility

Plastics News | August 2017 62